Drop Ruby 2.5 as well

Author: lsegal

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
       matrix:
         os: [ubuntu-20.04, macos-latest, windows-2019]
         # 3.0 is interpreted as 3
-        ruby: [2.5, 2.6, 2.7, "3.0", 3.1, 3.2, 3.3]
+        ruby: [2.6, 2.7, "3.0", 3.1, 3.2, 3.3]
         exclude:
           - { os: windows-2019, ruby: 2.2 }
           - { os: windows-2019, ruby: 2.3 }